From: Jesper Dangaard Brouer <brouer@redhat.com>
To: bpf@vger.kernel.org, Stanislav Fomichev <sdf@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
netdev@vger.kernel.org, martin.lau@kernel.org, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev,
song@kernel.org, yhs@fb.com, john.fastabend@gmail.com,
dsahern@gmail.com, willemb@google.com, void@manifault.com,
kuba@kernel.org, xdp-hints@xdp-project.net
Subject: [xdp-hints] [PATCH bpf-next V2 2/4] selftests/bpf: xdp_hw_metadata cleanup cause segfault
Date: Wed, 01 Feb 2023 18:31:55 +0100 [thread overview]
Message-ID: <167527271533.937063.5717065138099679142.stgit@firesoul> (raw)
In-Reply-To: <167527267453.937063.6000918625343592629.stgit@firesoul>
Using xdp_hw_metadata I experince Segmentation fault
after seeing "detaching bpf program....".
On my system the segfault happened when accessing bpf_obj->skeleton
in xdp_hw_metadata__destroy(bpf_obj) call. That doesn't make any sense
as this memory have not been freed by program at this point in time.
Prior to calling xdp_hw_metadata__destroy(bpf_obj) the function
close_xsk() is called for each RX-queue xsk. The real bug lays
in close_xsk() that unmap via munmap() the wrong memory pointer.
The call xsk_umem__delete(xsk->umem) will free xsk->umem, thus
the call to munmap(xsk->umem, UMEM_SIZE) will have unpredictable
behavior. And man page explain subsequent references to these
pages will generate SIGSEGV.
Unmapping xsk->umem_area instead removes the segfault.
Fixes: 297a3f124155 ("selftests/bpf: Simple program to dump XDP RX metadata")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
tools/testing/selftests/bpf/xdp_hw_metadata.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
index 3823b1c499cc..438083e34cce 100644
--- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
@@ -121,7 +121,7 @@ static void close_xsk(struct xsk *xsk)
xsk_umem__delete(xsk->umem);
if (xsk->socket)
xsk_socket__delete(xsk->socket);
- munmap(xsk->umem, UMEM_SIZE);
+ munmap(xsk->umem_area, UMEM_SIZE);
}
static void refill_rx(struct xsk *xsk, __u64 addr)
next prev parent reply other threads:[~2023-02-01 17:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 17:31 [xdp-hints] [PATCH bpf-next V2 0/4] selftests/bpf: xdp_hw_metadata fixes series Jesper Dangaard Brouer
2023-02-01 17:31 ` [xdp-hints] [PATCH bpf-next V2 1/4] selftests/bpf: xdp_hw_metadata clear metadata when -EOPNOTSUPP Jesper Dangaard Brouer
2023-02-01 17:31 ` Jesper Dangaard Brouer [this message]
2023-02-01 17:46 ` [xdp-hints] Re: [PATCH bpf-next V2 2/4] selftests/bpf: xdp_hw_metadata cleanup cause segfault Martin KaFai Lau
2023-02-01 17:53 ` Jesper Dangaard Brouer
2023-02-01 17:32 ` [xdp-hints] [PATCH bpf-next V2 3/4] selftests/bpf: xdp_hw_metadata correct status value in error(3) Jesper Dangaard Brouer
2023-02-01 17:32 ` [xdp-hints] [PATCH bpf-next V2 4/4] selftests/bpf: xdp_hw_metadata use strncpy for ifname Jesper Dangaard Brouer
2023-02-01 19:11 ` [xdp-hints] Re: [PATCH bpf-next V2 0/4] selftests/bpf: xdp_hw_metadata fixes series Stanislav Fomichev
2023-02-02 0:00 ` patchwork-bot+netdevbpf
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